The cutting of metals and other hard materials is often carried out with the use of a cutting tool to provide a desired shape, size or surface to the workpiece. When cutting these hard materials, frictional heat can burn the cutting tool and make the machined surface of the workpiece rough. Furthermore, thermal expansion lowers the accuracy of the shape and the size of the workpiece and the tool, thereby causing various other problems. To help alleviate the above problems, a cutting fluid is often employed during cutting.
Oils are commonly used as a cutting fluid when cutting metals and other hard materials. One disadvantage of using a straight oil as a cutting fluid is that it usually has to be used at low temperatures because high temperatures can cause the production of fire and smoke. To help overcome this problem, an oil-water emulsion cutting fluid having sufficient lubricity and cooling properties, can be used as a cutting fluid.
Unfortunately, cutting fluids, especially water-based cutting fluids, are susceptible to bacteria and other microbial propagation; Bacterial colonies often result in unpleasant odors, deterioration of the cutting fluid, and serious health hazards. In general, there are two types of bacteria that grow in cutting fluids: aerobic, which multiply in the presence of oxygen, and anaerobic, which propagate in the absence of oxygen. While the anaerobic types can result in unpleasant odors through the production of hydrogen sulfide, they typically do very little actual damage to cutting fluid itself. However, the aerobic type seriously degrades fluids, causing corrosion inhibition and loss of lubricity. Furthermore, the bacterial lifecycle while “eating” the fluid concentrate also results in the deposition of various acids and salts. This can cause extensive rusting/corrosion of both moving machine parts and the material being machined.
To prevent these accompanying problems, biocides have been added to cutting fluids. In practice however, these agents are of limited usefulness. In addition to costing more money, there are limits on the amount of biocide which can be incorporated into the cutting fluid. Furthermore, these agents are often ineffective, degrade over time, and replacing them can be expensive. In addition, these agents and substances often lower the quality of the cutting fluid.
Accordingly, there is a need in the art for an effective and new method of treating cutting fluids, that can provide uniform protection, or substantially uniform protection with time, without the use of large amounts of biocides.
Other distinct embodiments of the teachings herein pertain to the treatment of fountain solutions used in printing systems. In general, offset lithographic printing employs planographic plates which transfer ink via a blanket roll to a substrate thereby forming printed images. The plates are referred to as planographic because the image and non-image areas are in the same plane. The image areas, which accept ink, are distinguished from the non-image areas on the plate, by being oleophilic (having an affinity to oil), whereas the non-image areas are hydrophilic (water accepting).
Typically, a lithographic printing plate is covered with a thin film of fountain solution which prevents the ink from covering the plate in the non-image areas. More specifically, the fountain solution helps maintain the non-image areas of the printing plate, by increasing their hydrophilic nature.
Unfortunately, fountain solutions often provide a suitable medium for microorganisms to propagate. Unwanted microorganisms can include, bacteria, algae, mold, and the like, for example. To combat this problem, anti-microbial agents, or toxic biocides, can be added to the fountain solution.
While biocides added to fountain solution concentrates can afford protection to the product in storage and shipment, they are of limited usefulness after they have been diluted. Even in the diluted state, some of these biocides are skin sensitizers and higher dosages have been reported to cause skin sensitivity and other dermatological problems.
In order to avoid the toxic use of biocides, UV has been considered for the control of microorganisms in fountain solutions. Typical UV treatment involves killing microorganisms through lytic processes, wherein cell membranes and cellular components are decomposed. While UV light can function somewhat effectively in relatively clean water, when a solution is dirty or contains a number of compounds, the effectiveness of UV light decreases. This decrease in effectiveness generally occurs because these additional compounds in the solution absorb a significant amount of the UV energy. Furthermore, the use of UV rays can chemically or physically alter the fountain solution, such as to negatively effect its intended purpose.
Smith, in U.S. Pat. No. 6,503,449 discloses treating water-based suspensions with high-energy, low-frequency ultrasound. In addition to requiring high-energy, this process is dependent upon using toxic biocides to treat the suspensions.
Accordingly, there is a need in the art for an effective, low-energy, high-frequency method of treating fountain solutions without the use, or with limited use, of toxic biocides, and without compromising the effectiveness of the fountain solution. Furthermore, there is a need to provide a treatment that will provide microorganism control throughout the fountain solution system and in a manner which will provide substantially uniform protection with time.